Alloy



.im 12, 1932-. H. LQHMANN 1,840,457

' ALLOY Filed Jan. A16, 1926 Patented Jam-'12,1 1932 UNITED STATES HGO LOHMAN N, F BERLIN-JOHANNISTHAL, 'GERMAN Y Application led January 16, 1926, Serial No. 81,806, and in Germany January 24, 1925.

My invention relates to a new and improved method for' making the carbides of the relatively infusible metals.

One of the objects of my invention relates to anew and improved method for making I ferred to as heavy metals, because their atomic weights are respectively 184 and 96. Hence, whenever I refer to a tungsten carbide or a tungsten alloy, either in the description or in the claims, it is to be understood that 5 this includes a similar molybdenum alloy, or

an alloy containing both tungsten and molybdenum.

Another object of my invention is to provide a new and improved method for producing hard and stron masses or bodies of the carbides above mentioned so that these masses or bodies can .be utilized for various mechanical purposes, such as, for example, for manufacturing tools. y

Another object of my invention is to provide carbides of the relatively infusible metals and in particular a tungsten carbide in which the carbon is present in proper proportion.

Other objects of my invention will be set forth in the following description and drawings Which illustrates a preferred embodiment thereof, it being understood that the above general statement of the objects of my invention is intended merely to generally explain the same and not to limit it in any manner.

Fig. 1 is a diagrammatic side view, partially in section, showing a carbon tube furnace.

Fig. 2 is an end view of the device shown in Fig. 1.

Fig. 3 is a diagrammatic view showing the boat and casting mold.

Methods have been known for many years for making hard and strong articles composed of the carbides of the relatively insoluble metals, such as tungsten carbide.

According to these previously known methods, the metallic carbides were first manufactured by a melting process, they were then powdered and were then subjected to a second heattreatment with or without the addition of other substances. In this second heat treatment, the temperature of the mass was raised either to the melting point or almost up to the melting point. This method included two steps and had many disadvantages and it was not reliable, so that the products resulting therefrom were often worthless. In addition, it required the careful attention of highly skilled workmen.

According to my invention, I utilizea mixture of an oxygen compound of the metal, together with an additional metal or metallic compound, the melting 4point of said additional metal or metallic compound being as close as possible to the melting point of the tirst mentioned metal. This mixture is melted 1n the presence of carbon and is cast in molds,

the melted mass being removed as quickly as J possible from the furnace or heated space, to prevent an undesirable excess saturation of the product with carbon. This causes the excess carbon to be separated when the molten mass 'solidiies For example, an oxygen compound of the infusible metal, as, for example, tungstic acid or the anhydride, or highly reduced powdered metallic oxides, such as, for example, reduced metals which still contain a substantial proportion of oxygen can be mixed with a heavy metal or a compound thereof, such as, for example, thorium or uranium oxide or tantalum or a similar metal 0r metallic oxide. These additional metals also have high atomic weights and high melting points. Thus the atomic weight of thorium 1s 232.4, that of tantalum is 181.5, andthat of uranium is 238.5. While my invention generally relates to produce a dense, homogeneous alloy consisting of tungsten, carbon,l and a metal whose atomic weight is not less than that of tantalum (such as thorium), it is not restricted to an absolutely pure alloy. As above mentioned, these additional metals or metallic oxides have melting points which are the same or which are substantially the same as the metal whose carbide is to be formed. The mixture made as above specified is formed lao I .into a briquette by pressure. This briquette 1s now preferably heated in carbon vessels to whiclrthe molds are directely joined, in inclined carbon tube ovens until the desired 5 reaction-and melting temperature is attained. The carbon of which the vessels are made, as well as the carbon-containing gases present in the furnace or heated space, first reduces the metallic oxide o r oxides to the metallic form when the proper reaction temperature has been attained, and then produces the formation of the metallic carbide. .At the moment when the carbide is melted and for a short time thereafter, the metallic carbide has the desired proportion of or saturation ,with the carbon. The melted mass Hows immediately into the associated mold and fills the'mold. It is desirable to remove the mold together with the molten contents thereof out of the oven as soon as possible.

As shown in Figs. 1 and 2, a carbon tube furnace may be used having graphite electrodes a connected `to buss bars. A carbon tube b is also provided and the material to be treated is p ut into a boat d.

As shown in Fig. 3, the boat d in which the materialis melted may have a metal body f and it may be connected to a casting mold e.

I have discovered that if the metal is subjectedjfor a substantial period to the action of the carbon while the said metal 1s in the molten form, that the mixture is supersatu- 4rated with the carbon, and above the limit desired. If the molten mass is quickly removed from the oven, the excess carbon in the form of graphite is separated when the mass solidifies. The amount of carbon present in the carbide made according to my invention is between 4%% to 5%. For example 1f the carbide of tungsten is prepared accordmg to my invention, an alloy is produced which has very desirable properties. The use of tantalum (or of tantalum oxide, which is an equivalent) produces a particularly useful alloy.

If insteadA of employing the oxides of the infusible metals as in the example above given, thepure metal or4 the -metal in the commercial form is utilized (such as :tungsten, for example), it is not necessary to reduce the raw material so that theprocess can be carried out much more quickly. However, the reactions are substantially the same as those above described.

t I have discovered that when thorium carbide is mixed with tungsten and the mixture When this mixture is melted (as for example, the mixture of tungsten and thorium lcarbide) the thorium carbide at once yields my process, it is preferable to use 100 parts by Weight of solid raw tungsten, 5 to 10 parts by weight of thorium carbide, and 3 to 5 parts by weight of molybdenum.

Unsaturated thorium carbide, which iS present in the mixture, makes'it extremely hard and tough, which are decided advantages. If the tungsten contains some oxygen, then the thorium carbide simultaneously reduces the'oxide which is present tothe metallic state. Y

I have shown a preferred embodiment of my invention, but it is clear that numerous changes and omissions could' be made Without departing from its spirlit..

Claims: I

1. As a new article of manufacture, a dense and homogeneous alloy consisting substantially of tungsten, carbon, and tantalum, the tungsten comprising the major portion of the alloy, and the percentage of carbon being not less than four per cent.

' 2. As a new article .ogf manufacture, a Hdense -HUGO LOI-IMANN.

In testimony whereof I aiix my signature. I.

is-melted in the retorts, that very hard and mechanically irm bodies are .produced which have an absolutely homogeneous structure,

especially if a small amount of molybdenum is- 60 added to the mixture. The thorium carbide can contain from 12% to .14% of carbon. Hence, the carbon for producing the tungstenniarbde is partially secured from the thorium carbide mixed therewith as above 

